Due to their long lifetime, small size, high resistance to shock and vibration, low heat generation, and low power consumption, light emitting diodes (LEDs) have been widely used in display or as light source in various consumer electronic devices, electrical appliances, and apparatuses. Recently, multi-color and high brightness LEDs have also been used in out-door large-screen displays, traffic lights, etc. In the future, LEDs may act as the major illumination light source, with the advantages of energy saving as well as environment protection.
One common type of LED is the white LED, which is capable of emitting white light. Different approaches can be implemented to realize white light emitting from an LED. One approach is to use the combination of a blue LED chip and yellow phosphor. FIG. 1 shows the cross-sectional view of a prior art white LED. The conventional white LED 100 shown in FIG. 1 comprises a blue LED chip 110 arranged on a base 120. The blue LED chip 110 is electrically connected to the base 120 by electrical wires W. A yellow phosphor resin 130 is formed to cover the blue LED chip 110 and the wires W by dispensing, for example. A lens 140 is formed over the yellow phosphor resin 130. The blue light emitted by the blue LED chip 110 is partially absorbed by the yellow phosphor powders in the yellow phosphor resin 130 and converted to yellow light. Unabsorbed blue light mixes with the yellow light so as to generate a white light.
However, there are problems with such convention LEDs in that it is often difficult for the yellow phosphor resin 130 formed by dispensing to evenly cover the LED chip. A thicker portion of the yellow phosphor resin 130 absorbs more blue light and emits more yellow light than a thinner portion. Accordingly, it is difficult for such an LED 100 to emit light with uniform color. For example, while it may be possible to realize white light in the center portion of the yellow phosphor resin 130, light emitted from other portion of the yellow phosphor resin 130 may undesirably appear yellowish.